=Paper=
{{Paper
|id=Vol-2177/paper-10-a002
|storemode=property
|title=
Success Access Probability Analysis Using Virtual Preambles Via Random Access Channel
|pdfUrl=https://ceur-ws.org/Vol-2177/paper-10-a002.pdf
|volume=Vol-2177
|authors=Ivan E. Sinitsyn,Elvira R. Zaripova,Yulia V. Gaidamaka,Vsevolod S. Shorgin
}}
==
Success Access Probability Analysis Using Virtual Preambles Via Random Access Channel
==
https://ceur-ws.org/Vol-2177/paper-10-a002.pdf
67
UDC 621.39
Success Access Probability Analysis Using Virtual Preambles
Via Random Access Channel
Ivan E. Sinitsyn* , Elvira R. Zaripova* ,
Yulia V. Gaidamaka*† , Vsevolod S. Shorgin†
*
Department of Applied Probability and Informatics
Peoples’ Friendship University of Russia (RUDN University)
6 Miklukho-Maklaya st., Moscow, 117198, Russian Federation
†
Institute of Informatics Problems, Federal Research Center
"Computer Science and Control" of the Russian Academy of Sciences
44-2 Vavilova st., Moscow, 119333, Russian Federation
Email: iesinitsyn@gmail.com, zaripova_er@rudn.university,
gaydamaka_yuv@rudn.university, vshorgin@ipiran.ru
Now rapid growth of number of the devices communicating among themselves in LTE
(Long-Term Evolution) communication networks is observed, especially growth of number
of machine-to-machine (M2M) devices should be noted because the number of devices will
exceed 50 billion in recent years.
To simplify low-cost network connection of a set of devices, communications of machine
type (Machine-type communications, MTC) evolved in low-cost MTC (LC-MTC) in 3GPP
standarts. LC-MTC have to cope with intensive access through a set of narrow-band channels
of random access (RACH) of LTE frequencies appropriated in the range effectively. With
increase in quantity and density of placement of MTC-devices the scheme of random access for
LC-MTC RACH has to be improved. In this paper we suggest to use the concept of virtual
preambles in the random access procedure and we carry out the success access probability
and an average delay analysis via a random access channel.
Key words and phrases: random access channel, collision, access success probability,
low-cost MTC, preamble.
Copyright © 2018 for the individual papers by the papers’ authors. Copying permitted for private and
academic purposes. This volume is published and copyrighted by its editors.
In: K. E. Samouylov, L. A. Sevastianov, D. S. Kulyabov (eds.): Selected Papers of the VIII Conference
“Information and Telecommunication Technologies and Mathematical Modeling of High-Tech Systems”,
Moscow, Russia, 20-Apr-2018, published at http://ceur-ws.org
68 ITTMM—2018
1. Introduction
Machine-to-machine communications are extremely important for effective data
transmission from devices in a communication network for ensuring various services of
the Internet of Things, for example, such as applications for the smart house, logistic
tracking, health care, safety, observation and clever measurement [1–5]. It is expected
that more than 50 billion devices will be connected to network to serve the needs of
Internet of Things and the demand for the effective systems of MTC communications
considerably will increase [2]. The 3rd Generation Partnership Project (3GPP) has
started process of standardization of machine-type communications based on LTE and
LTE-Advanced technologies. MTC is standardized in the 10th release (Release-10) and
evolved in low-cost MTC (LC-MTC) in release 13 for cost-effective connectivity at a
large number of MTC devices.
To reduce the cost of LC-MTC equipment the 3GPP RAN working group has offered
new structure of RACH where the LTE network appropriates several narrow-band
random access channels (NarrowBand-RACH, NB-RACH) within its bandwidth. The
LC-MTC device chooses one of available NB-RACH channels, performing a session
initiation procedure for the chosen RACH channel. Unlike the classical procedure
where the MTC device doesn’t choose the physical channel, in new structure with the
additional identifier the choice of the concrete channel can reduce the collisions arising at
session initiation procedure. Thus, introduction of additional identifiers will reduce the
consumed amount of energy [6]. The growing number of MTC devices has led to many
studies being carried out on alleviation of overloads and on reduction of the possible
collisions emerging at session initiation on a radio channel of RACH [7].
Standard solutions on alleviation of possible overloads in RACH can be two types:
based on push and pull technology. In the decisions based on push technology, the
procedure of session initiation is started by autonomous requests from MTC devices.
For avoidance of collisions each MTC device has to generate a unique preamble for
session initiation within the restrictions [8], predetermined or provided by network,
besides sending a preamble is possible in a certain time-slot (Access Grant Time Interval,
AGTI) [9]. In the decisions based on pull technology, the session initiation procedure is
operated by commands of the base station (eNodeB, eNB). The base station synchronizes
access for each MTC device or group of devices via the paging channel. Then the MTC
devices are only called to initiate the procedure of random access [10].
In this paper the concept of virtual preambles for more effective recognition of
LC-MTC devices and reduction of collisions is offered.
2. Concept of Virtual Preamble
The session initiation procedure, by the so-called rule of four handshakes, assumes
successful sending a preamble on the first step and successful reception of the response
message of RAR (Random-Access-Response) on the second step.
The existing session initiation procedure on a radio channel of RACH means existence
of 𝑁𝑝𝑟 preambles, 𝑁𝑃 𝑅𝐴𝐶𝐻 physical channels PRACH (Physical Random Access
Channel) for sending a preamble and PDCCH channel (Physical Downlink Control
Channel) on the descending communication line for a mandrel of the response message
of RAR.
The new scheme session initiation offered for LC-MTC RACH uses new channel
EPDCCH (Enchanced Physical Downlink Control Channel) which number can be the
additional identifier in a so-called virtual preamble instead of PDCCH channel [2]. The
sheaf with the EPDCCH channel number increases quantity of virtual preambles by the
coefficient equal to the number of EPDCCH channels, Fig. 1.
For LC-MTC the device can choose the EPDCCH channel number for the response
message of RAR, then for the base station such preamble will differ from other pream-
bles [2]. In the existing scheme of a preamble transfer from the MTC device to the
base station for the existing session initiation procedure without binding to the PRACH
Sinitsyn Ivan E. et al. 69
index. In the presence of one identifier with number of a preamble perhaps at once of
time it is unique to distinguish no more than 𝑁𝑝𝑟 preambles. In the presence of the
second identifier in the form of EPDCCH channel the base station will distinguish a
preamble by not only according to her number but on a linking of number of a preamble
with the virtual identifier of EPDCCH channel. When receiving two preambles with one
number of a preamble the base station will distinguish these preambles on the virtual
identifier of EPDCCH channel, and such approach will reduce the arising collisions that
will serve increase in success access probability, reduction of average access delay and
other measures.
Figure 1. Virtual preambles identifications
The number of virtual identifiers of a preamble can linearly be scaled with the number
of the integrated indexes of PRACH. In the offered LC — MTC RACH structure each
EPDCCH channel can be logically connected to several PRACH channels.
In the course of session initiation the virtual preamble actually isn’t transferred, but
implicitly distinguished between the base station and LC-MTC devices. Therefore the
LC-MTC devices using the offered scheme can be compatible to those MTC devices
which use the outdated scheme of session initiation.
3. Success access probability and average delay analysis
We analyze the following measures: collision probability, defined as the ratio between
the number of occurrences when two or more MTC devices send a random access
attempt using exactly the same preamble and the overall number of opportunities (with
or without access attempts) in the period; access success probability, defined as the
probability to successfully complete the random access procedure within the maximum
number of preamble transmissions; an average access delay, defined as the delay for each
random access procedure between the first random access attempt and the completion
of the random access procedure, for the successfully accessed MTC devices.
The dependence of session initiation procedure measures on a collision probability
is investigated in [1]. The same methods of a Markov chain construction were applied
in [11–13]. An influence of introduction of the additional identifier of EPDCCH channel
on these characteristics remains interesting.
The success access probability is presented by a formula (1) [1]:
𝑃 (𝜔) = 1 − (𝑝 + (1 − 𝑝)𝑔 𝑀 +1 )𝑁 +1 (1)
70 ITTMM—2018
where 𝑝 — the collision probability of a preamble, and 𝑔 — probability of unsuccessful
transfer of the HARQ message Msg3, 𝑁 and 𝑀 — restrictions for the number of
retranslations of a preamble and the HARQ message respectively. The probability of a
preamble collision 𝑝 is estimated by a formula (2) [8]:
𝑝 = 1 − 𝑒𝛾/𝐿 (2)
where 𝛾 — intensity of session initiation requests.
Number 𝐿 — of the reserved session initiation opportunities (attempts) in a second
is presented by formula (3) [14]:
𝐿 = 𝑁𝑐ℎ * 𝑁𝑝𝑟 * 200. (3)
Also we analyse an average session initiation delay 𝐷 using formula (4) [1]:
𝑔 − (𝑀 + 1) 𝑔 𝑀 +1 + 𝑀 𝑔 𝑀 +2
𝐷 = (∆1 +∆3 +∆4 ) + ∆4 · +
(1 − 𝑔) (1 − 𝑔 𝑀 +1 )
𝛽 1 − (𝑁 + 1) 𝛽 𝑁 + 𝑁 𝛽 𝑁 +1
(︀ )︀
+ (∆1 +∆2 ) · +
(1 − 𝑝) (1 − 𝑔 𝑀 +1 ) (1 − 𝛽 𝑁 +1 )
𝑔 𝑀 +1 1 − (𝑁 + 1) 𝛽 𝑁 + 𝑁 𝛽 𝑁 +1
(︀ )︀
+ (∆3 + 𝑀 ∆4 − ∆2 ) · , (4)
(1 − 𝑔 𝑀 +1 ) (1 − 𝛽 𝑁 +1 )
where 𝛽 = 𝑝 + 𝑔 𝑀 +1 (1 − 𝑝) is the probability of preamble retransmission.
4. Numerical experiment
We analyze the dependence of a collision probability (Fig. 2)and success access
probability (Fig. 3) on number of LC-MTC devices in a cell and number of EPDCCH
channels on which RAR messages are transferred. Data from Table 1 is used for
estimations.
With introduction of the additional identifier in the form of the EPDCCH channel
number reduction of collision probability and increase in success access probability in
connection for the subsequent transfer of small data is observed. Graphics in Fig. 2 and
Fig. 3 𝑁𝑐ℎ = 1 show measures for the existing session initiation procedure.
All measures change their values when we apply an additional EPDCCH channel.
For the case 𝑁𝑐ℎ = 2 for 7 000 LC-MTC devices the collision probability of a preamble
will decrease by 1.7 times. Let us show results for the case with two additional EPDCCH
channels. For this case with 30 000 LC-MTC devices the collision probability falls from
value 0.95 to 0.62, at the same time the success access probability rises up from value
0.45 to 0.99.
Average access delay is also decreasing with the growth of number of physical channels
as shown on Fig. 4 for 30 000 LC-MTC devices average access delay with 𝑁𝑐ℎ = 1 equals
142 ms, for 𝑁𝑐ℎ = 2 channels the value is lower by 1.5 times and for 𝑁𝑐ℎ = 3 channels
the value drops by 2.15 times.
5. Conclusions
The additional identifier approach allows to reduce the collision probability that
influences all the indicators participating in the session initiation procedure for MTC
devices on RACH radio channel. Introduction of additional identifiers increases the
success access probability and reduces the average access delay. The analysis of success
access probability and average delay is shown in the current paper.
As further research we plan to apply this approach for analysis of new RACH
mechanisms, for example, so called CAM RACH (critical alarm messages RACH) for
Emergency Alarm Messages, or to another preliminary measures [15–22].
Sinitsyn Ivan E. et al. 71
Table 1
Random access related system parameters
Parameters Notation Value
Total number of RACH opportunities 𝐿 10800; 21600; 32400
Maximum number of preamble (Msg1) 𝑁 90
retransmissions
Maximum number of HARQ retrans- 𝑀 250
missions for Msg3
Total number of preambles in a RA slot 𝑁𝑝𝑟 240
Probability of unsuccessful transfer of 𝑔 130
the HARQ message (Msg3)
Number of physical channels 𝑁𝑐ℎ 1; 2; 3
Time interval before sending Msg3 or ∆1 10.5 ms
preamle retransmission
Time interval for Backoff window ∆2 20 ms
Time interval between successful receiv- ∆3 5 ms
ing Msg2 and sending Msg3
Time interval for sending Msg3, waiting ∆4 6 ms
and processing Msg4
Figure 2. Collision probability
72 ITTMM—2018
Figure 3. Success access probability
Figure 4. Average access delay
Sinitsyn Ivan E. et al. 73
Acknowledgments
The publication has been prepared with the support of the “RUDN University
Program 5-100” and funded by RFBR according to the research projects No 17-07-00845,
16-07-00766.
References
1. K. E. Samouylov, Y. V. Gaidamaka, I. A. Gudkova, E. R. Zaripova, S. Y. Shorgin,
Baseline Analytical Model for Machine-Type Communications over 3GPP RACH in
LTE-Advanced Networks, T. Czachórski et al. (Eds.): ISCIS 2016, CCIS 659 (2016)
203–213.
2. J. S. Kim, S. Lee, M. Y. Chung, Efficient Random-Access Scheme for Massive
Connectivity in 3GPP Low-Cost Machine-Type Communications, IEEE Transactions
on Vehicular Technology 66 (7) (2017).
3. M. Islam, A. E. Taha, S. Akl, A Survey of Access Management Techniques in
Machine Type Communications, IEEE Communications Magazine, 52 (4) (2014)
74–81.
4. 3GPP TS 22.368 v13.1.0, Technical Specification Group Services and System Aspects;
Service Requirements for Machine-Type Communications (MTC); Stage 1 (Release
13), Dec. 2014.
5. A. Metnitzer, Nokia Siemens Networks Machine2Machine Solution, In Proc. Inter-
national Convention of MIPRO, May 2011, pp. 386–388.
6. T. Taleb and A. Kunz, Machine Type Communications in 3GPP Networks: Potential,
Challenges, and Solutions, IEEE Communications Magazine 50 (3) (2012) 178–184.
7. M. Hasan, E. Hossain, and D. Niyato, Random Access for Machineto-Machine
Communication in LTE-Advanced Networks: Issues and Approaches, IEEE Com-
munications Magazine 51 (6) (2013) 86–93.
8. 3GPP TR 37.868 v11.0.0, Technical Specification Group Radio Access Network;
Study on RAN Improvements for Machine-type Communications, Sep. 2011.
9. S. Y. Lien, K.-C. Chen, and Y. Lin, Toward Ubiquitous Massive Accesses in 3GPP
Machine-to-Machine Communications, IEEE Communications Magazine 49 (4)
(2011) 66–74.
10. C. H. Wei, R. G. Cheng, and S. L. Tsao, Performance Analysis of Group Paging for
Machine-Type Communications in LTE Networks, IEEE Transactions on Vehicular
Technology 62 (7) (2013) 3371–3382.
11. A. Ometov, E. Sopin, I. Gudkova, S. Andreev, Y. V. Gaidamaka, Y. Koucheryavy,
Modeling Unreliable Operation of mmWave-Based Data Sessions in Mission-Critical
PPDR Services, IEEE Access 5 (2017), art. no. 8055435, pp. 20536-20544.
12. D. Efrosinin, K. Samouylov, I. Gudkova, Busy period analysis of a queueing system
with breakdowns and its application to wireless network under licensed shared access
regime, Lecture Notes in Computer Science (including subseries Lecture Notes in
Artificial Intelligence and Lecture Notes in Bioinformatics), LNCS 9870 (2016)
426–439.
13. K. Samouylov, V. Naumov, E. Sopin, I. Gudkova, S. Shorgin, Sojourn time analysis
for processor sharing loss system with unreliable server, Lecture Notes in Computer
Science (including subseries Lecture Notes in Artificial Intelligence and Lecture
Notes in Bioinformatics) 9845 (2016) 284–297.
14. Ericsson R1-061369 TSG-RAN WG1 45 LTE random-access capacity and collision
probability, Shanghai, China, May 8–12, 2006.
15. D. Sijabat, R. Harwahyu and R. G. Cheng, Energy-Efficiency of RACH-Based small
data transmission scheme in LTE networks, 2017 40th International Conference on
Telecommunications and Signal Processing (TSP), Barcelona (2017) 106–109.
16. N. Jiang, Y. Deng, M. Condoluci, W. Guo, A. Nallanathan and M. Dohler, RACH
Preamble Repetition in NB-IoT Network, in IEEE Communications Letters, no. 99
(2018) 1–11.
74 ITTMM—2018
17. A. H. E. Fawal, A. Mansour, F. Le Roy, D. Le Jeune and A. Hamié, RACH overload
congestion mechanism for M2M communication in LTE-A: Issues and approaches,
2017 International Symposium on Networks, Computers and Communications
(ISNCC), Marrakech (2017) 1–6.
18. S. Vural, N. Wang, P. Bucknell, G. Foster, R. Tafazolli and J. Muller, Dynamic
Preamble Subset Allocation for RAN Slicing in 5G Networks, in IEEE Access 6
(2018) 13015–13032.
19. K. Taleb Ali, S. Ben Rejeb and Z. Choukair, A congestion control approach based on
dynamic ACB of differentiated M2M services in 5G/HetNet, 2017 13th International
Wireless Communications and Mobile Computing Conference (IWCMC), Valencia
(2017) 1126–1131.
20. V. Schrader, M. Vilgelm and W. Kellerer, On Random Access Channel Performance
and M2M Support in Standalone LTE Unlicensed, GLOBECOM 2017 — IEEE
Global Communications Conference, Singapore (2017) 1–7.
21. L. Tian, C. Yan, W. Li, Z. Yuan, W. Cao and Y. Yuan, On uplink non-orthogonal
multiple access for 5g: opportunities and challenges, in China Communications
14 (12) (2017) 142–152.
22. Chih-Min Chao and Chia-Tsun Chen, Ratio adjustable channel hopping enhancement
for heterogeneous cognitive radio networks, 2017 IEEE International Conference on
Communications Workshops (ICC Workshops), Paris (2017) 1093–1098.